Parts Needed to Add 3rd Brake Light to Small Utility Trailer with 4-Pole Wiring

Question: You explained about installing a converter to split the brake/turn signal in a one wire system. But upon looking at the wiring diagram after the converter I have to splice back into the yellow and green wires prior to the tail light and install diodes to prevent back feeding. my question is would it not work fine without the diodes and not splice back into the yellow and green wires. the out side of the converter would hook back up to yellow and green respectively, and the third wire direct to the extra brake light. Wouldnt this serve the same purpose without the extra splice and diodes? my third brake light is LED and others are incandesent bulbs. I was all set to order the parts but thought of this. thanks


Expert Reply:

To add a 3rd brake light to a trailer's existing lighting will require a signal converter to separate out the brake signal from the turn signals that are combined by trailer wiring. You need the converter # 118158 to provide a brake-only output signal to prevent the 3rd brake light from flashing like a turn signal.

In your particular application you will not need diodes but you may need a load resistor # P230004C to let the high-efficiency LED brake light function correctly with other incandescent lights. The load resistor will let the LED light appear to have a similar electrical resistance to the incandescent lights. You will connect the load resistor and 3rd light to the red wire on the converter.

The wiring may be easier if you use a junction box like # 38656 and ring terminals like # DW05739-1.

expert reply by:
Adam R

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